Satellite communications (SATCOM) systems or networks enable communication at very long distances, typically referred to as over-the-horizon or beyond-line-of-sight communications. A SATCOM system typically includes one or more satellites orbiting the earth. The satellites direct data and voice traffic between terminals located on earth. Transception of data over SATCOM systems must comply with certain standards and access protocols that are suitable for the type of data to be transmitted. The access protocol determines how channel bandwidth will be allocated among system users.
One widely used satellite channel access communication protocol is Demand Assigned Multiple Access (DAMA). The DAMA technique matches user demands to available satellite capacity. Satellite resources are grouped together as bulk assets, and the DAMA protocol assigns users satellite resources (communication circuits, timeslots, channels, and the like) on a per-request basis matching user information transmission requirements. Once communication is complete, the satellite resources are returned to a pool of available satellite resources for assignment to other users. Since the limited number of satellite resources is used according to need, a DAMA protocol can effectively increase the number of users and provide easier access to the satellite resources for the users. By using DAMA, many users can be served using only a fraction of the satellite resources required by dedicated, point-to-point-single-channel-per-carrier networks, reducing the costs of satellite networking.
Ultra High Frequency (UHF) SATCOM operations provide military users with long-haul data and voice communications capability. In order to enable secure, high capacity communications, and terminal interoperability, standards have been developed to specify the performance characteristics and channel access protocols that user terminals must possess in order to be certified for UHF SATCOM operations. Terminals certified for UHF SATCOM operations must be capable of employing a Demand Assigned Multiple Accesses (DAMA) protocol. In addition, certified terminals must be capable of meeting defined encryption requirements, as well as meeting transmission rates and power requirements. These DAMA certified terminals, which operate in the 5 and 25 kHz bandwidth UHF range, are governed by United States Military Standard (MIL-STD) 188-181, MIL-STD-188-182 and, MIL-STD-188-183. DAMA certified terminals must negotiate for the use of SATCOM resources using the conventional DAMA orderwire, and this negotiation must be done at a data rate of 9600 bits-per-second (bps) using compatible cryptography.
Many SATCOM terminals meet these requirements and are interoperable with the DAMA UHF SATCOM system. Unfortunately, however, some user terminals (referred to herein as “disadvantaged terminals”) cannot interoperate with a DAMA UHF SATCOM system because, for example, they do not support compatible cryptography, they do not have sufficient transmit power, and/or they cannot meet the 9600 bps data rate requirements. Some exemplary disadvantaged terminals include handheld combat search and rescue radios, personnel recovery radios, blue force tracking system, sensors, and the like. The primary characteristics that cause a terminal to be a disadvantaged terminal are their small form factor and/or low radio frequency power output which prevents full implementation of MIL-STD-188-181/182/183.
In certain instances it would be highly advantageous for selected disadvantaged terminals to attain over-the-horizon communications through a DAMA-controlled UHF SATCOM system. Such a scenario may be in the search and rescue of a radio user, such as a downed pilot, in hostile territory. However, such a feature should concurrently preserve efficient allocation of the extremely scarce SATCOM resources.